A switching power supply of a non-linear control type (for example, fixed on-time type, fixed off-time type or hysteresis window type) is characterized in that, compared with a switching power supply of a linear control type (for example, voltage mode control type or current mode control type), high load response characteristics can be obtained with a simpler circuit configuration.
Such a switching power supply may also have a function of detecting a backflow of a coil current when there is a light load to forcibly turn off a synchronous rectification transistor (a so-called backflow blocking function).
However, the conventional switching power supply has a problem in that switching between a continuous current mode (a heavy load state in which no backflow blocking operation is performed) and a discontinuous current mode (a light load state in which a backflow blocking operation is performed) is not smoothly performed such that the backflow blocking operation is intermittently performed and an output ripple increases.